1. Field of Invention
This invention relates to a method of improving the image quality in a nuclear magnetic resonance (hereinafter called "NMR") tomographic device.
2. Description of the Prior Art
In a NMR tomographic device, it is necessary to correct for phase distortion of data resulting from the characteristics of the device upon re-constituting an image. One of the typical scanning methods used in NMR is the Fourier method, wherein phase correction is exclusively conducted by computation for absolute value. That is, assuming the real part is Rij and the imaginary part is Zij, for the image data represented by the complex number obtained by subjecting the scanned data to a 2-dimensional inverse Fourier transformation, an iamge Pij to be displayed is usually calculated as follows ##EQU1## wherein i, j represent piccel numbers.
In this method, however, in case of a pulse sequence where negative data are obtained, as in the inversion recovery method (IR method), the data are turned back to the positive side which results in difficult observation of the image. In view of the foregoing, in a phase stable system, a phase .theta. can be previously determined under the same condition by some appropriate means and correction can be made using the phase .theta. as follows EQU Pij=Rij.multidot.cos .theta.+Zij.multidot.sin .theta.
However, since the magnitude of rotation of the phase is generally location dependent (which can not be corrected completely by this method) there occurs an undesired shading in the image, and density distortion due to uneven sensitivity of receiving coils or the like. These cannot be readily corrected.